(1) Field of the Invention
The present invention relates to a liquid crystal display device.
(2) Related Art Statement
As a result of progress in technology for manufacturing liquid crystal panels in recent years, liquid crystal display elements have been used as displays for televisions, the majority of which were conventionally cathode ray tubes. Twisted nematic (TN) mode display systems are known as conventional liquid crystal display elements, and in these systems, it has been an object to improve the contrast, view angle properties and response (=response time). In particular, the response, which is a factor dominating the quality of moving images, is inferior to that of cathode ray tubes when applied to televisions, and thus, improvement has been strongly desired.
Concerning the response, it is known, as described in Non-Patent Document 1, that the viscosity and the elastic constant of the liquid crystal material are control factors. Meanwhile, it is necessary for such parameters as anisotropy in the index of refraction, which are optical properties, nematic-isotropic transition temperature, which are temperature properties, and anisotropy in the dielectric constant, which are electrical properties, to be balanced when a liquid crystal material is used for a display. However, when any one parameter is changed, other parameters may also change. Therefore, it becomes very difficult to adjust the balance with other parameters when the viscosity or elastic constant is changed greatly in order to improve the response.
So far it has only been possible to improve the response by improving the display system and the drive system, in addition to the viscosity and the elastic constant. In recent years, however, it has been reported that the response can be improved by adding nanoparticles to liquid crystal as non-liquid crystal components. For example, the results of improvement in the response time of liquid crystal display devices by adding a material having anisotropy in the uniaxial form to liquid crystal have been reported as organic nanoparticles, as in Non-Patent Documents 2 and 3.
(Non-Patent Document 1) Chemistry of Liquid Crystal, Edited by The Chemical Society of JAPAN, p. 46, 1994
(Non-Patent Document 2) Collection of Abstracts for IDW by Sang Youn Jeon et al., pp. 167-170, 2005
(Non-Patent Document 3) SID Digest by Scott J. Woltman et al., pp. 752-755, 2005